Currently, one of the main steps in the manufacture of semiconductor devices is the formation of metal and dielectric thin films on a substrate by a gaseous chemical reaction. This deposition process includes a chemical vapor deposition (CVD). In a typical thermal CVD process, reactant gases are provided to the surface of a substrate, and a predetermined thin film is formed on the surface of the substrate due to the occurrence of a thermally-induced chemical reaction. A thermal CVD process is conducted at a high temperature, and a device having the layer formed on the substrate may be damaged due to the high temperature. One of the methods capable of solving such a problem, that is, among methods in which metals and dielectric films are deposited at a relatively low temperature, is a plasma enhanced CVD (PECVD) method.
According to plasma enhanced CVD technology, radio frequency (RF) energy is applied to a reaction zone, and this promotes the excitation and/or dissociation of reactant gases, thereby generating plasma with highly reactive species. The high reactivity of the species in plasma reduces the energy required for a chemical reaction to take place and thus lowers the temperature required by the process. Semiconductor device structures have significantly decreased in size due to the introduction of this apparatus and method.
Meanwhile, silicon dioxide (SiO2), which has been mainly used as an interlayer insulating film until now, has a resistance-capacitance (RC) delay time when ultra-large scale integrated circuits of 0.5 μm or less are manufactured. Therefore, in order to reduce the RC delay of the multilayer metal film used for integrated circuits of a semiconductor device, research on the formation of an interlayer insulating film used for metal wires with a material having a low relative dielectric constant (k≦3.5) have recently been actively conducted. Such a thin film having a low dielectric constant is formed either with an inorganic material such as a fluorine (F)-doped oxide film (SiOF) and a fluorine-doped amorphous carbon (a-C:F) film, or with an organic material including carbon (C).
Materials having a low dielectric constant currently considered for use as a substitute for SiO2 include SILK (available from DOW Chemical), FLARE (fluorinated poly(arylene ether), available from Allied Signals) and the like, which are mainly formed by spin coating, and SiOF, Black Diamond (available from Applied Materials), Coral (available from Novellus) and the like, which are formed by chemical vapor deposition (CVD). In addition, organic polymers such as polyimide, and porous thin film materials such as xerogel or aerogel are also included.
Herein, the material having a low dielectric constant, which is formed using a spin casting method in which the material is cured after being spin coated, is formed to a dielectric substance having a low dielectric constant since pores having a size of few nanometers (nm) are formed within the film resulting in the density decrease in the thin film. Generally, the polymers deposited by spin coating have advantages in that they usually have a low dielectric constant and excellent planarization. However, polymers are not suitable to be applied to a semiconductor since they have a heat-resistant threshold temperature lower than 450° C., thereby having poor thermal stability, and particularly, polymers have various problems in the manufacture of devices since the mechanical strength of the thin film is low due to the size of the pores being large and the pores not being uniformly distributed within the film. In addition, polymers have problems in that they have poor contact with upper and lower wiring materials, and high stress due to thermal curing. Further, the reliability of devices is reduced due to dielectric constant changes attributable to the absorption of water present in the surroundings.
Meanwhile, the inventors of the present invention have conducted a study on a thin film using a PECVD method with hexamethyldisiloxane and 3,3-dimethyl-1-butene as precursors, and considerably improved the dielectric constant of the thin film (Korean Patent Number 10-0987183). However, there remained a problem in that the mechanical properties of the thin film were not satisfactory.